The present invention is directed towards a protective bypass for electronic circuits and, more particularly, to a bypass which enables a plurality of circuit breakers to be shortcircuited to one another when the circuit breakers are first connected to an electrical circuit being protected.
Circuits of the foregoing type are generally known. A prior art circuit sold by Lutron Electronics Co., Inc., the assignee of the present invention, is illustrated in FIGS. 1-3. As shown therein, a bypass circuit 10 is connected to a lighting circuit 12 which includes a dimmer module 13 including three dimmer circuits 14A, 14B and 14C (hereinafter referred to generally as dimmer circuits 14), a bank of circuit breakers 16a, 16b and 16c (hereinafter referred to generally as circuit breakers 16) and a plurality of loads 18A, 18B and 18C (hereinafter referred to generally as loads 18) typically fluorescent or incandescent lamps. The dimmer circuits 14A, 14B and 14C are connected to loads 18A, 18B and 18C via circuit breakers 16A, 16B and 16C, respectively. The remaining ends of each load 18 is connected to an a.c. power source 20 which, in turn, is connected to the common circuit breaker 16I. The remaining end of the circuit breaker 16I is connected to the dimmer circuits 14A-14C so as to form a closed circuit. So connected, each dimmer circuit 14A-14C will control the amount of power applied to its respective load 18A-18C in a manner well known in the art. Each of the load circuit breakers 16A-16C will trip whenever the current in its associated load 18A-18C exceeds a predetermined value so as to protect the load from overcurrents. In a similar manner, input circuit breaker 16I will trip whenever the main current to the dimmer circuits 14A-14C exceeds a predetermined value.
When initially wiring the light circuit 12, it is desirable to protect the dimmer circuits 14 against miswiring or shortcircuits since the dimmer circuits are relatively expensive. This is accomplished by providing a bypass circuit 10 which directly connects the input circuit breaker 16I to each of the load circuit breakers 16A, 16B and 16C. This shorts or bypasses the dimmer circuits 14 but still ensures that the circuit breakers are available to protect the loads 18.
As best shown in FIGS. 1 and 2, the prior art bypass circuit 10 includes a plurality of terminal blocks 22A, 22B and 22C (hereinafter referred to generally as blocks 22) each of which selectively shortcircuits the input circuit breaker 16I to a respective one of the load circuit breakers 16A, 16B and 16C. Each terminal block 22 is formed by a pair of insulative housings 24 having lugs 26, 28 formed at opposite ends thereof. Each pair of lugs 26, 28 formed in the same insulative housing 24 are electrically coupled to one another. As best shown in FIG. 2, each lug 26 includes a set screw 30 which can be used to retain a conductive bypass circuit wire 34 in mechanical and electrical contact with the conductive lug 26. A similar set screw 32 is provided for each lug 28.
As best shown in FIGS. 1 and 3, the rightmost insulative housing 24 of each terminal block 22 is coupled to the circuit breaker lug 36 of input circuit breaker 16I while the leftmost insulative housing 24 of each terminal block 22 is connected to the circuit breaker lug 36 of a respective load circuit breaker 16A, 16B, 16C. The remaining lugs 28 of each pair of insulative housings 24 defining a respective terminal block 22 are shortcircuited by a U-shaped jumper 40. As best shown in FIG. 3, a respective set screw 44 associated with each lug 36 releasably holds both a bypass circuit wire 34 and a dimmer module wire 54 in the lug 36. So connected, the terminal blocks 22A, 22B and 22C shortcircuit the input circuit breaker 16I to each of the load circuit breakers 16A, 16B and 16C, respectively. This protests the dimmer circuits 14A, 14B and 14C against miswires and shortcircuits and at the same time ensures that the circuit breakers 16 protect the loads 18.
While the foregoing circuitry provides adequate protection for the dimmer circuits 14, it is disadvantageous in that it requires a significant amount of space and labor. Additionally, since separate wires 34, 54 are provided to connect the circuit breakers 16 to the dimmer module 13 and to connect the circuit breakers 16 to the bypass circuit 10, and since the separate wires terminate at the same circuit breaker lugs 36, it is not possible to remove the dimmer module 13 to repair or replace it without disrupting the bypass wiring.